Feature tracker (3.7.0)

[quinchs]

Summary

On the 19th Discord added some new features to their api, this issue is a tracker for all the new features added.

• thread.create_timestamp - discord/discord-api-docs@53ee010 #436
• message create flags - discord/discord-api-docs@95816a5 #437
• guild widgets - discord/discord-api-docs@e0e2f21 #438
• filename regex - discord/discord-api-docs@5868a2b #439
• guild welcome screen - discord/discord-api-docs@00a0ae2 #440
• remove stage discovery - discord/discord-api-docs@8b2b155 #441

ontop of these features labs is behind from discord.net and needs to be crossmerged.